1. Technical Field
The invention relates to interchangeable and relatively inexpensive mold tooling for injection-molded articles.
2. Background Art
Existing molding technology has enabled the production of thin-wall commercial bumper fascias that are manufactured by the use of the reaction injection molding (RIM) method, the thermoplastic injection molding (TIM) method or the thermoformed sheet molding (TFSM) method. Large molded articles, such as bumper fascias for commercial trucks are extremely large compared to other molded components and require relatively large tooling to produce the parts. For example, commercial truck bumper fascias are generally eight feet wide, two feet high and three feet deep. These thin-wall articles are generally molded as one main piece with additional, smaller components assembled to the main part for strength and rigidity.
While all of the current production technologies are capable of molding the large fascia part, the parts that are produced do not have the inherent strength and stability to be mounted directly onto a vehicle. The parts from all of the molding technologies are very dependant on additional plastic and metal components such as reinforcements and braces to achieve the strength and the stability to enable them to be mounted onto a truck. In the case of the RIM parts, because of the fact that this is a very low pressure process, surface voids and porosities need to be filled before the parts are primed and painted. Since all of these technologies only produce an outer skin, a further drawback to the RIM fascias, the normal TIM fascias and the TFSM fascia parts is their fragility to impact failures when mounted on a vehicle. And finally, because of the additional components and labor that are necessary to complete these fascias, their costs need to be reflected in the final pricing of the subassemblies.
The mold tooling for a commercial truck fascia of this size, that is necessary to support these processes, is very large and unique to each manufacturing process in terms of complexity and the resultant expense. Beginning with the simplest and least expensive tooling for the TFSM method, progressing to the middle-priced low pressure tooling for the RIM method and finally to the most expensive high pressure molds for the TIM method, the number of incorporated part features that are possible to incorporate into the molded part increases from one process to the next with the very best features and molding materials being available from the TIM process. Since the RIM tooling and the TIM molds can provide similar features in the molded part, it becomes a natural desire to gain the benefits of the TIM process at the tooling price of the RIM molds, a combination that has not been possible previously. The financial implications of this disparity become even more severe when the production life of the tooling must be amortized over a relatively small number of parts that will be produced from that tooling over the limited life of the project.
TIM mold blocks for large articles such as commercial truck bumper fascias are expensive due to the size and the intricate design criteria. Additionally, the size of these mold blocks typically results in very limited portability, thereby often requiring dedicated tooling and possibly dedicated presses. When one mold for a commercial truck bumper fascia, in an injection press, is changed out for another commercial truck bumper fascia mold, dedicated tooling and plumbing are required. It is a very cumbersome and dangerous process to change over the molds and tooling, in an injection press, and requires a great deal of time resulting in significant costs associated with tooling, labor, and down time of the press.
The prior art has provided interchangeable molds for relatively smaller components. Such interchangeable molds are typically directed to molds that include multiple sub-molds, inserts, for molding multiple smaller articles in each cycle. The prior art interchangeable molds include an interchangeable insert that is constrained about its complete periphery where the host mold blocks provide for the complete interface with the injection-molding machine from the supply of all utility fluids and functions, the flow path of the molten material to the ejection system that removes the molded parts from the inserted cavities. In essence, the prior art interchangeable mold is assembled outside of the machine and is then installed into the molding machine as a functioning unit.